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Study of damage to a high concrete dam subjected to underwater shock waves

Earthquake Engineering and Engineering Vibration 2014年第2期13卷 337-346页

作者： Lu Lu Li Xin Zhou Jing Faculty of Architecture and Civil Engineering Huaiyin Institute of Technology The State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

To study the effect of a strong underwater shock wave on a concrete dam, this research aims to improve hammer impact methods in model tests. Six 1:200 scale models were designed and tested under distributed impact loads. A device was deployed for a direct measurement of the impact force at the upstream face of the dams. The model dam bases were anchored to prevent displacement. The experimental results indicate that the top part of the concrete dam is a weak zone, and the impact failure initiates with a fracture on the top of the dam. The peak value of impact stress increases when the second crack appears in the concrete dam from the upstream face to the downstream face. And, the level of the second crack in the dam body is lower as the peak value of impact stress increases. In this study, dynamic analysis was conducted by calculating the results to verify the effectiveness of a device to directly measure the impact force. This method may be used to approximately forecast the damage of concrete dam and may also be useful in other engineering applications.

关键词： underwater shock wave hammer impact impact force high concrete gravity dam forecast damage

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Non-spherical symmetry development of underwater shock waves created by laser-induced breakdown

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Journal of Hydrodynamics 2023年第1期35卷 76-82页

作者： Ying-xue Wang Di-xi Han Jian-hua Liu Qiang Zhong Zhi-feng Yao Ruo-fu Xiao Fu-jun Wang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China China Ship Scientific Research Centre Wuxi214082China Taihu Laboratory of Deepsea Technological Science Wuxi214082China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing100083China

As a controllable alternative to cavitation collapse-induced shock waves,numerous cavitation studies on laser-induced breakdown have been carried out in *** the laser focusing region is not spherical,the shock waves caused by laser breakdown also exhibit non-spherical symmetry ***,some researchers have proposed the linear superposition theory based on the far field measurement data to explain this asymmetry,assuming that it is essentially the linear superposition of multiple wave fronts caused by multiple points of laser-induced breakdown that leads to the asymmetric propagation of shock *** this study,measurements of shock wave propagation processes with different breakdown energies are carried out based on a nanosecond resolution photogrammetry system,and the propagation velocities of shock waves in different directions are directly measured using a double exposure technique on a single *** the experiment,the velocity of the shock wave at the beginning of the breakdown was measured up to nearly 4000 m/*** early shock wave front was ellipsoidal,and the propagation velocity in the laser incident direction was generally slower than that in the perpendicular direction,decaying to the speed of sound in water within 1000 ns after the breakdown,and the wave front gradually approached to a *** variability of the shock wave front pressure ratio in the laser propagation direction and the vertical direction implies that the linear superposition theory applicable to the far field is not applicable to the near *** may be more complex mechanism for the near-field shock wave propagation process.

关键词： underwater shock wave non-spherical symmetry velocity decay linear superposition laser breakdown

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Numerical simulation for deformation of multi-layer steel plates under underwater impulsive loading

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Journal of Harbin Institute of Technology(New Series) 2012年第3期19卷 68-72页

作者：任鹏张伟郭子涛魏刚 Hypervelocity Impact Research Center Harbin Institute of Technology

To further understand the dynamic deformation and impact resistance of thin-plate hull structure under impulse wave,the deformation of multi-layer steel plates under underwater impulsive loading has been studied by AUTODYN *** order to verify the validity of numerical methods,the experimental results are compared with the simulation *** multi-layer plate types include 1 mm + 3 mm,2 mm + 2 mm,3 mm + 1 mm double-layer,and 4 mm monolayer annealed 304 stainless steel *** type of target plates has four flyer plate's *** are 150,200,250 m /s and 300 m /*** pressure wave histories in water and deformation of specimens have been predicted and measured by numerical *** simulation results demonstrate that the protective capacity of 2mm + 2mm double-layer annealed 304 stainless steel plates is the best one in this velocity range of flyer plate,as the integral deformation is the smallest among the four structure types.

关键词： underwater shock wave numerical simulation thin plate structure dynamic response

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Momentum Transfer on underwater shock Generation Induced by Pulsed Laser Irradiation with Thin Metal

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Open Journal of Fluid Dynamics 2016年第3期6卷 166-181页

作者： Rokhsan Ara Hemel Hiroyuki Hirahara Kento Takahashi Graduate School of Science and Engineering Saitama University Saitama Japan Faculty of Engineering Saitama University Saitama Japan

The present paper has investigated the momentum transport phenomena of underwater shock wave generation in terms of photo-acoustic wave with a very thin metal. The shock wave was induced by a pulsed-laser irradiation. In order to clarify the momentum transport mechanics in this phenomenon, we have been considered the momentum and energy transport from laser to metal, and metal to water. A numerical solution of thermo-elastic wave in metal has been obtained to estimate a fundamental gain of the longitudinal wave. Then, the underwater shock wave phenomena have been analyzed by adapting compressible fluid dynamics with suitable boundary condition between the solid and liquid. We had performed an experiment as well and observed the shock wave with optical system. The aim of the research is to estimate the underwater shock wave strength theoretically. The metal region was calculated by Laplace transformation of heat conduction and wave equations. The water region was simulated by MacCormack’s method. Some of boundary conditions have been examined and the acceleration condition has been adopted at the interface. The simulated results show a good agreement with experimental result, consequently the momentum transfer mechanism from longitudinal wave to underwater shock wave has been cleared in the present report.

关键词： Momentum transfer underwater shock wave Longitudinal wave

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Hydrodynamic Characteristics and Supercavity Shape of Supercavitating Projectiles Launched with Supersonic Speed

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Journal of Marine Science and Application 2022年第2期21卷 24-33页

作者： Chuang Huang Kaixin Guo Kan Qin Kai Luo Daijin Li Jianjun Dang School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an710072China

A supercavitating projectile is launched underwater with supersonic speed,and then,the speed decreases to transonic and subsonic conditions orderly because of the drag coming from surrounding *** flow regime and hydrodynamic characteristics are significantly influenced by the flying speed,the influence laws in supersonic,transonic,and subsonic regions are totally *** issues aren’t well studied.A numerical model consisting of VOF model,moving frame method and state equation of liquid is established to calculate the compressible supercavitation flow field,and validated by comparing with a published *** influences of water compressibility and Mach number on supercavity shape and hydrodynamic characteristics are quantitatively *** results show that the flying speed of supercavitating projectiles exerts significant influences on the flow regime,supercavity shape and hydrodynamic characteristics for the transonic and supersonic *** the decrease of flying speed,the drag coefficient decreases gradually,and the dimensions of the supercavity near supercavitating projectiles significantly increases in the high-speed *** underwater bow shock is numerically observed before the disk cavitator in supersonic ***,no obvious changes are found for the incompressible water cases with different *** supersonic conditions,the supercavity near supercavitating projectiles of compressible water is smaller than that of incompressible water,the drag coefficient is larger,and the relative difference significantly increases with the flying *** the case of Ma 1.214,the relative difference of supercavity diameter at the tail section 3.98%,and the difference of the drag coefficient is 23.90%.

关键词： Supersonic projectiles Compressible water underwater shock wave Supercavity Hydrodynamic characteristics

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